buttond - button handling daemon

simple evdev daemon that reads a /dev/input/eventX file and runs configured action if configured key has been pressed for configured time

Quick start

Identify input device

Find what input device events come from. It is recommended to use stable paths for devices, e.g. the /dev/input/by-* symlinks.
For example, we have here an usb keyboard and an internal switch (gpio):

$ ls -l /dev/input/by-*/*
...
lrwxrwxrwx 1 root root 9 Mar  3 10:14 /dev/input/by-id/usb-0566_3029-event-kbd -> ../event2
lrwxrwxrwx 1 root root 9 Mar  3 10:09 /dev/input/by-path/platform-gpio-keys-event -> ../event1

If you do not recognize any name here just try them all, for example the following command will listen for events on all input devices and display them along with the filename the event came from (run, push button and stop buttond with ctrl+C when done):

$ buttond -vvv /dev/input/event*

Identify key

Find what key you want. Running with -vv will display ignored keys.
Run buttond with -vv and press key you want to bind to display its name, then stop buttond with ctrl+C:

$ buttond -vv /dev/input/by-path/platform-gpio-keys-event
[11340.668] PROG1 (148) pressed: ignored
[11340.928] PROG1 (148) released: ignored

Define actions/run service

Device what you want to do and do it: e.g. "restart service foo if key pressed shortly, and poweroff if pressed longer than 10 seconds" (default for long key is 5s):

$ buttond /dev/input/by-path/platform-gpio-keys-event \
	-s prog1 -a "rc-services foo restart" \
	-l prog1 -t 10000 -a "poweroff"

Notes

Multiple actions for a key:
- short keys are handled when released, if released within timeout (default 1s). There can be only one.
- the longest long key is handled as soon as timeout (default 5s) elapses.
  For example, the above example will run poweroff as soon as 10s ellapsed, without waiting for key release.
- if there are multiple long keys, time at release time is checked and the longest action whose timeout is shorter than hold time is executed, if any.
  For example, -s x -a action0 -l x -a action1 -l x -t 10000 -a action2 would:
  - keypress < 1s: run action0 on release
  - keypress >= 1s, <5s: do nothing
  - keypress >= 5s, <10s: run action1 on release
  - keypress >= 10s: run action2 10s after pushdown
Key source does not matter, if you have two devices which use the same key code start buttond once for each device instead.
Key presses are debounced. Releasing the key for less than 10ms will not trigger anything, and keep counting time from initial key press.
Actions "on release" actually happen 10ms after release.
For devices that might disappear (e.g. usb keyboard), it's possible to use -i <file> to use inotify to wait for it to come back

atmark-techno / buttond